/*
 * Copyright 2023 OPS4J.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.keycloak.adapters.osgi;

import org.keycloak.adapters.KeycloakConfigResolver;
import org.keycloak.adapters.KeycloakDeployment;
import org.keycloak.adapters.OIDCHttpFacade;

import java.net.URI;
import java.util.ArrayList;
import java.util.List;

/**
 * This {@link KeycloakConfigResolver} tries to resolve most specific configuration for given URI path. If not found,
 * <em>parent</em> path is checked up to top-level path.
 */
public class HierarchicalPathBasedKeycloakConfigResolver extends PathBasedKeycloakConfigResolver {

	public HierarchicalPathBasedKeycloakConfigResolver() {
		prepopulateCache();
	}

	@Override
	public KeycloakDeployment resolve(OIDCHttpFacade.Request request) {
		// we cached all available deployments initially and now we'll try to check them from
		// most specific to most general
		URI uri = URI.create(request.getURI());
		String path = uri.getPath();
		if (path != null) {
			while (path.startsWith("/")) {
				path = path.substring(1);
			}
			String[] segments = path.split("/");
			List<String> paths = collectPaths(segments);
			for (String pathFragment: paths) {
				KeycloakDeployment cachedDeployment = super.getCachedDeployment(pathFragment);
				if (cachedDeployment != null) {
					return cachedDeployment;
				}
			}
		}

		throw new IllegalStateException("Can't find Keycloak configuration related to URI path " + uri);
	}

	/**
	 * <p>For segments like "a, b, c, d", returns:<ul>
	 *     <li>"a-b-c-d"</li>
	 *     <li>"a-b-c"</li>
	 *     <li>"a-b"</li>
	 *     <li>"a"</li>
	 *     <li>""</li>
	 * </ul></p>
	 * @param segments
	 * @return
	 */
	private List<String> collectPaths(String[] segments) {
		List<String> result = new ArrayList<>(segments.length + 1);
		for (int idx = segments.length; idx >= 0; idx--) {
			StringBuilder sb = null;
			for (int i = 0; i < idx; i++) {
				if (sb == null) {
					sb = new StringBuilder();
				}
				sb.append("-").append(segments[i]);
			}
			result.add(sb == null ? "" : sb.substring(1));
		}
		return result;
	}

}
